[MM-53454] Add export file settings + slash command for public link (#23915)

Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/config.go

@@ -1546,6 +1546,22 @@ type FileSettings struct {
 	AmazonS3SSE                        *bool   `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
 	AmazonS3Trace                      *bool   `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
 	AmazonS3RequestTimeoutMilliseconds *int64  `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	// Export store settings
+	DedicatedExportStore                     *bool   `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
+	ExportDriverName                         *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
+	ExportDirectory                          *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3AccessKeyId                *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3SecretAccessKey            *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3Bucket                     *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3PathPrefix                 *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3Region                     *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3Endpoint                   *string `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3SSL                        *bool   `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
+	ExportAmazonS3SignV2                     *bool   `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
+	ExportAmazonS3SSE                        *bool   `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
+	ExportAmazonS3Trace                      *bool   `access:"environment_file_storage,write_restrictable,cloud_restrictable"`
+	ExportAmazonS3RequestTimeoutMilliseconds *int64  `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
+	ExportAmazonS3PresignExpiresSeconds      *int64  `access:"environment_file_storage,write_restrictable,cloud_restrictable"` // telemetry: none
 }
 
 func (s *FileSettings) SetDefaults(isUpdate bool) {
@@ -1653,6 +1669,68 @@ func (s *FileSettings) SetDefaults(isUpdate bool) {
 	if s.AmazonS3RequestTimeoutMilliseconds == nil {
 		s.AmazonS3RequestTimeoutMilliseconds = NewInt64(30000)
 	}
+
+	if s.DedicatedExportStore == nil {
+		s.DedicatedExportStore = NewBool(false)
+	}
+
+	if s.ExportDriverName == nil {
+		s.ExportDriverName = NewString(ImageDriverLocal)
+	}
+
+	if s.ExportDirectory == nil || *s.ExportDirectory == "" {
+		s.ExportDirectory = NewString(FileSettingsDefaultDirectory)
+	}
+
+	if s.ExportAmazonS3AccessKeyId == nil {
+		s.ExportAmazonS3AccessKeyId = NewString("")
+	}
+
+	if s.ExportAmazonS3SecretAccessKey == nil {
+		s.ExportAmazonS3SecretAccessKey = NewString("")
+	}
+
+	if s.ExportAmazonS3Bucket == nil {
+		s.ExportAmazonS3Bucket = NewString("")
+	}
+
+	if s.ExportAmazonS3PathPrefix == nil {
+		s.ExportAmazonS3PathPrefix = NewString("")
+	}
+
+	if s.ExportAmazonS3Region == nil {
+		s.ExportAmazonS3Region = NewString("")
+	}
+
+	if s.ExportAmazonS3Endpoint == nil || *s.ExportAmazonS3Endpoint == "" {
+		// Defaults to "s3.amazonaws.com"
+		s.ExportAmazonS3Endpoint = NewString("s3.amazonaws.com")
+	}
+
+	if s.ExportAmazonS3SSL == nil {
+		s.ExportAmazonS3SSL = NewBool(true) // Secure by default.
+	}
+
+	if s.ExportAmazonS3SignV2 == nil {
+		s.ExportAmazonS3SignV2 = new(bool)
+		// Signature v2 is not enabled by default.
+	}
+
+	if s.ExportAmazonS3SSE == nil {
+		s.ExportAmazonS3SSE = NewBool(false) // Not Encrypted by default.
+	}
+
+	if s.ExportAmazonS3Trace == nil {
+		s.ExportAmazonS3Trace = NewBool(false)
+	}
+
+	if s.ExportAmazonS3RequestTimeoutMilliseconds == nil {
+		s.ExportAmazonS3RequestTimeoutMilliseconds = NewInt64(30000)
+	}
+
+	if s.ExportAmazonS3PresignExpiresSeconds == nil {
+		s.ExportAmazonS3PresignExpiresSeconds = NewInt64(21600) // 6h
+	}
 }
 
 type EmailSettings struct {